RESUMO
Background: Mapuche, Chilean natives, represent approximately 9.8 pecent of Chilean population and in the IX region of the country, they account for 18.4 percent of population over 15 years old. They preserve some socio-cultural characteristics that make them different to the rest of the population. Aim: To describe the epidemiological characteristics rheumatoid arthritis among Mapuche natives. Subjects and methods: Retrospective review of patients of Mapuche origin with rheumatoid arthritis, seen at Temuco Hospital between 1980 and 1996. Results : Among 308 cases gathered, only 106 (93 women, aged 55 ñ 10 years old) complied with 1987 American College of Rheumatology (ACR) criteria for rheumatoid arthritis. The disease began between 29 and 52 years old in 73 percent of patients and the mean delay in diagnosis was 4.4 years. At diagnosis, 99 percent had symmetric poliarthritis, 28.3 percent had either fatigue, fever or weight loss, and 46.9 percent were in class III or in class IV of ACR-1991. Fifty three percent of patients developed Sicca syndrome, 36 percent developed nodules, 23 percent developed Raynaud phenomenon, 11 percent developed pulmonary involvement, 7 percent developed vasculitis, 5 percent developed neurological manifestations and 19 percent developed ophthalmologic involvement. Rheumatoid factor was positive in 78 percent and 73 percent had erosions. HLA DR4 was (+) in 60 percent of 30 patients. Thirty percent required 3 or more disease modifying drugs and prednisone over 10 mg/day. There was no correlation between functional capacity and several other features of the disease. Conclusions: Mapuche rheumatoid arthritis patients are detected late and have a poor functional capacity at the time of diagnosis. They also have a higher proportion of extraarticular manifestations, more erosions and require more aggressive treatments